Hocus pocus is a purported magical phrase in the style of rhyming
and alternating incarnations taken from grimoires. The origin of the term
is uncertain, and some have come to believe it means utter nonsense. One
origin is attributed to Ochus Bochus, a legendary magician and demon of
the Norse. During the reign of King James I of England, the term hocus pocus
was accredited to a self-styled magician, according to A Candle in the Dark:
or a Treatise Concerning the Nature of Witches and Witchcraft (1656) by
Thomas Ady:

I will speak of one man who called himself "The King's Majesties
most excellent Hocus Pocus," and so he was called, because that at
the playing of every Tricke, he used to say, "Hocus pocus tonus,
talontus, vade celeriter jubeo," a dark composure of words to blind
the beholders, to make his trick to pass more currently without discovery.

More likely, hocus pocus is a corruption and mockery of the Latin hoc
est enim corpus meum ("this is [indeed] my body") spoken by
the priest in the Catholic Mass. Many Protestants think hocus pocus concerning
the substantiation, changing of the bread and wine into the body and blood
of Christ, of the Catholic Mass, too
much like magic.

Hocus pocus is said not to be associated with magic or Witchcraft but
with trickery, stage-magic, conjuring,
and deceit. Some of these latter activities are associated with sorcery, sometimes referred to a low magic performed
for self-gain. A.G.H.